首先摆几个公式.
S=1/2*a*b*sin(A);
cos(A)=(b*b+a*a-c*c)/2/a/b;
cos(A)*cos(A)+sin(A)*sin(A)=1;
#include
#include
int main()
{
float a,b,c;
float cosA,sinA,S;
while(scanf("%f%f%f",&a,&b,&c))
{
if(a>=b+c || b>=a+c || c>=a+b)
printf("数据有问题\n");
else
{
cosA=(float)(b*b+a*a-c*c)/2/a/b;
sinA=sqrt(1-cosA*cosA);
S=0.5*a*b*sinA;
printf("%f\n",S);
}
}
}
